Process for the production of integral color correction masks



United States Patent 3 Claims. ((31. 96-9) This invention relates to a process of color correction of subtractive colors in color photographic multilayer materials by forming integral color correction masks in the layer. This is accomplished by reacting the residual color couplers with diazonium compounds derived from an amino salicylic acid.

In color photographic processes the ability of color couplers to react with the oxidation products of a color forming developer in particular primary aromatic amino developers is utilized for the production of subtractive color images. The subtractive colors are yellow, magenta and cyan. Generally the yellow color coupler is incorporated into the blue-sensitive layer, the magenta color coupler into the green-sensitive layer and the cyan color coupler into the red-sensitive layer. Whereas the yellow dyestuff corresponds approximately to theoretical requirements necessary for its light absorption, this is not the case with the cyan and the magenta dyestuffs. The deficiency of the cyan and magenta color couplers lead to errors in the color reproduction. Attempts have been made to correct these errors by producing colored masks for the transparent color negatives, which masks are to compensate for these incorrect absorptions and thus eliminate the incorrect control of the printing light. The masking images are formed in the photographic layers in the form of so-called integral color correction masks. The masking images which are produced are of a contrast opposite in sign to that of the partial images, since the density of the masking dye in any area of the layer is inversely proportional to the density of the dye of the primary partial image.

Many processes have been described for the production or" integral masking images. In one of these processes the residual color couplers which remain in the colordeveloped photographic layers are transformed into dyes by reaction with diazonium salts.

However, these diazonium salts are very unstable, both in the solid and in the dissolved forms. Use has been made in this connection of diazonium compounds in the form of zinc chloride double salts. However, this process also offers no satisfactory result as regards the stability of the solutions. It is frequently also impossible in this case to exclude the yellow coupler from the undesired co-coupling.

It is an object of this invention to provide a method of correcting the undesired absorption of the magenta and cyan partial image in the multilayer color photographic material. Another object is to provide diazonium compounds which are stable in solid and in dissolved form and which yield excellent masking images. Other objects will be apparent from the following description of the invention.

We now have found that all of these disadvantages can be avoided by using a diazonium salt of an amino salicylic acid as reaction component for the residual color coupler to form a masking image.

Diazonium salts which are derived from aminosalicylic acids in solid form are quite resistant to shock, and stable in solid and dissolved form. According to a preferred embodiment of this invention the stability and storability can be improved quite considerably by mixing the diazonium compounds with alkyl-naphthalene sulfonic acids. Suitable sulfonic acids are, for example: diisobutyl-naphthalene sulfonic acid.

The proportions of the diazonium salt and the alkyl naphthalene sulfonic acid is not critical and can be selected in accordance with the properties of the diazonium compound. It has been found that generally from about 0.1 part by weight to about 1 part by weight of the alkyl naphthalene sulfonic acid per part by weight of the diazonium compound are quite sufiicient to obtain the desired improvement of the stability.

The diazonium salts of aminosalicylic acids are particularly advantageous in that they do not react with the residual color-coupler for the yellow partial image. On the other hand they form a yellow dyestufi with the residual coupler for the magenta-colored partial image and, in the case of substitution by nitro groups, they form a reddish-violet dyestuff with the residual coupler for the cyan partial image.

Particular utility is shown by diazonium salts derived from aminosalicylic acid of the following formula NHt wherein R=hydrogen, alkyl preferably alkyl having up to 3 carbon atoms or nitro. Suitable compounds are:

2-hydroxy-3-nitro-5-aminobenzoic acid 2-hydroxy-4-rnethyl-5-a1ninobenzoic acid 2-hydroxy-3-amino-5-nitrobenzoic acid 2-hydroxy-3-amino-5-methylbenzoic acid Z-hy-droxy-S-aminobenzoic acid The preparation of the diazonium salts is carried out in the same way for all the derivatives and is explained, by way of example, by reference to the preparation of 2-hydroxy-3-nitro-5-aminobenzoic acid:

30 g. of 2-hydroxy-3-nitro-5-aminobenzoic acid are stirred into 180 cc. of concentrated hydrochloric acid, ice is added thereto and then cc. of 10% sodium nitrite solution are added dropwise at 05 C.

The mixture is then stirred for another hour and finally the diazonium salt is suction-filtered. The salt obtained is first of all washed with 600 cc. of alcohol and then with 300 cc. of ether. About 30 g. of dry diazonium salt are obtained. This is mixed with finely powdered sodium diisobutylnaphthalene sulfonate in a ratio by weight of 1:1.

The diazonium salt mixture is used either after the usual color processing in a special bath, advantageously at pH 5.5, or it is added to a photographic processing bath, e.g., a bleaching bath, and the operation can in this way be effected without using an additional bath.

The process of the invention can be applied to any conventional color photographic materials which contain magenta and/ or cyan color couplers capable of reacting with the oxydation products of primary aliphatic amino developers to form a dye. Preferred are color photographic materials which contain the color couplers in a diffusion-resistant form. Suitable are color couplers which are substituted by long-chain aliphatic groups and water solubilizing groups and which are distributed homogeneously in the layer, as well as color couplers which are soluble in organic solvents in which they are first dissolve-d and which combination is then dispersed in a finely divided state throughout the emulsion layer. Suitable solvents for this purpose are, for example, tries-ters of phosphoric or diesters of phthalic acids.

Suitable are the usual aromatic amino developers such as p-phenylendiamin type developers, especially the N,N- dialkyl-p-phenylen diamines. The process of the present invention can generally be used for compensating the undesired absorption of the dyes produced by reaction of usual cyan or magenta couplers the oxidation products of color-forming developers. Such magenta couplers are, for example, those derived from pyrazolone, in particular l-phenyl-pyrazolone as described, for example, in British Patent No. 892,886, indazolones, cyan acetyl substituted cumarones or cyan acetyl substituted benezenes or benzimidazolopyrazolones such as described in British Patent No. 918,128. We furthermore refer to the publication of O. Wahl in Zeitschrift fiir angew-andte Chemie, vol. 64 (1952), pages 259-265.

Cyan couplers which can be reacted with the diazonium compounds according to the process of the present invention are particularly phenol or naphthol couplers.

Example 1 An exposed multilayer color photographic film, of which the blue-sensitive silver halide layer contains 4-stearoyl aminobenzoylacetanilide 3', 5 dicarboxylic acid, the green-sensitive layer contains 1-(4'phenoxy-3'- sulfo)-phenyl-3-stearyl-5-pyrazolone, and the red-sensitive silver halide emulsion layer contains 2'-N-methyl-N- octadecyl-5-sulfo-l-hydroxynaphthoic acid-(2)-anilide, is processed as follows:

(1) Color development bath, 6 minutes- Water, cc. 1,000 p-Diethylaminoaniline sulfate, g. 5 Potassium carbonate, g 75 Anhydrous sodium sulfite, g. 2

The film is rinsed between the baths and after passing through the masking bath. After this processing, the film contains a yellow masked image in the magenta image layer, in addition to the partial image, and a reddishviolet masked image in the cyan image layer.

Example 2 Layer structure of the color film and color development bath as in Example 1.

(2) Bleaching bath, 5 minutes, pH 5.5- Water, cc. 1,000 Potassium ferricyanide, g. 100 Potassium bromide, g. 15 Mixture of diazonium salt of 2-hydroxy-3-nitro-5- aminobenzoic acid with sodium diisobutylnaphthalene sulfonate (1:1), g. Anhydrous sodium acetate, g 5

After the fixing, the same result is obtained as in Example 1.

4 Example 3 If the diazonium salt of 2-hydroxy-4-methyl-S-aminobenzoic acid is used as masking component and if the processing step is carried out as in Example 1 or 2, the processed film contains a positive yellow masking image and a negative magenta image in the green-sensitive layer.

Example 4 The diazonium salt of 2-hydroxy-3-amino-S-nitrobenzoic acid is used as masking component. After processing as in Example 1 or 2, a yellow masking image is obtained in the magenta layer and a reddish-violet masking image in the cyan layer.

Example 5 The diazonium salt of 2-hydroxy-3-amino-5-methylbenzoic acid is used as masking component. Processing as in Example 1 or 2 provides a yellow masking image in the magenta layer.

Example 6 The diazonium salt of 2-hydroxy-5-aminobenzoic acid is used. After processing as described in Example 1 or 2, a yellow masking image is obtained in the magenta layer.

We claim:

1. In the process of producing integral color masking images in a multilayer color photographic material by developing with a primary aromatic amino color-forming developer an imagewise exposed multilayer color photographic material comprising a silver halide emulsion layer sensitive to blue light and containing a color coupler that reacts with the oxidation products of said developer to form a yellow dye, a silver halide emulsion sensitive to green light and containing a color coupler that reacts with the oxidation products of said developer to form a magenta dye, and a silver halide emulsion layer sensitive to red light and containing a color coupler that reacts with the oxidation products of said developer to form a cyan dye, and treating the developed material with at least one aqueous bath containing a diazonium salt, the improvement according to which the diazonium salt is adiazonium salt of an aminosalicylic acid.

2. The combination as defined in claim 1, wherein the diazonium salt of the aminosalicylic acid corresponds to the formula wherein R stands for a substituent of the group consisting of hydrogen, alkyl having up to 3 carbon atoms and nitro.

3. The combination as defined in claim 2, wherein the treatment is performed with an aqueous bath containing an effective amount of the diazonium salt of a nitro substituted amino-salicylic acid.

References Cited by the Examiner UNITED STATES PATENTS 2,629,658 2/ 1953 Sprung 969 2,663,637 12/1953 Ganguin et al. 969

NORMAN G. TORCHIN, Primary Examiner.

I. TRAVIS BROWN, Assistant Examiner. 

1. IN THE PROCESS OF PRODUCING INTEGRAL COLOR MASKING IMAGES IN A MULTILAYER COLOR PHOTOGRAPHIC MATERIAL BY DEVELOPING WITH A PRIMARY AROMATIC AMINO COLOR-FORMING DEVELOPING AN IMAGEWISE EXPOSED MULTILAYER COLOR PHOTOGRAPHIC MATERIAL COMPRISING A SILVER HALIDE EMULSION LAYER SENSITIVE TO BLUE LIGHT AND CONTAINING A COLOR COUPLER THAT REACTS WITH THE OXIDATION PRODUCTS OF SAID DEVELOPER TO FORM A YELLOW DYE, A SILVER HALIDE EMULSION SENSITIVE TO GREEN LIGHT AND CONTAINING A COLOR COUPLER THAT REACTS WITH THE OXIDATION PRODUCTS OF SAID DEVELOPER TO FORM A MAGNETA DYE, AND A SILVER HALIDE EMULSION LAYER SENSITIVE TO RED LIGHT AND CONTAINING A COLOR COUPLER THAT REACTS WITH THE OXIDATION PRODUCTS OF SAID DEVELOPER TO FROM A CYAN DYE, AND TREATING THE DEVELOPED MATERIAL WITH AT LEAST ONE AQUEOUS BATH CONTAINING A DIAZONIUM SALT, THE IMPROVEMENT ACCORDING TO WHICH THE DIAZONIUM SALT IS A DIAZONIUM SALT OF AN AMINOSALICYLIC ACID. 